Answer:
3. Form 1040X, Schedule C, and any other forms or schedules affected by the change in his income.
Step-by-step explanation:
This question is missing the possible answers:
- Form 1040X. 
 -  Form 1040X and a copy of his original return. 
 - Form 1040X, Schedule C, and any other forms or schedules affected by the change in his income. 
 - Form 1040X, Schedule C, and a copy of each receipt left off the original return
 
The IRS requests that any change or amendment to a tax return must include a copy of all the tax forms and/or schedules that were presented with the original filing that is being amended. If the amendment affects more than 1 filing, you must include all the forms and schedules that were filed before and are being affected by the amendment.